Current fluctuations for TASEP: A proof of the Pr\"{a}hofer--Spohn conjecture

TL;DR

This paper proves a long-standing conjecture about the fluctuation behavior of the height function in TASEP with two-sided Bernoulli initial conditions, linking it to shock waves, rarefaction fans, and last passage percolation models.

Contribution

It provides a rigorous proof of the Pr"{a}hofer--Spohn conjecture, characterizing fluctuation orders and scaling functions for TASEP and related last passage percolation models.

Findings

Confirmed the fluctuation order and scaling functions for TASEP height fluctuations.

Established a fluctuation theorem for last passage times with two-sided boundary conditions.

Connected TASEP fluctuations to random matrix theory via Wishart ensemble perturbations.

Abstract

We consider the family of two-sided Bernoulli initial conditions for TASEP which, as the left and right densities ($\rho_-,\rho_+$) are varied, give rise to shock waves and rarefaction fans---the two phenomena which are typical to TASEP. We provide a proof of Conjecture 7.1 of [Progr. Probab. 51 (2002) 185--204] which characterizes the order of and scaling functions for the fluctuations of the height function of two-sided TASEP in terms of the two densities $\rho_-,\rho_+$ and the speed $y$ around which the height is observed. In proving this theorem for TASEP, we also prove a fluctuation theorem for a class of corner growth processes with external sources, or equivalently for the last passage time in a directed last passage percolation model with two-sided boundary conditions: $\rho_-$ and $1-\rho_+$. We provide a complete characterization of the order of and the scaling functions for the fluctuations of this model's last passage time $L(N,M)$ as a function of three parameters: the two boundary/source rates $\rho_-$ and $1-\rho_+$, and the scaling ratio $\gamma^2=M/N$. The proof of this theorem draws on the results of [Comm. Math. Phys. 265 (2006) 1--44] and extensively on the work of [Ann. Probab. 33 (2005) 1643--1697] on finite rank perturbations of Wishart ensembles in random matrix theory.